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Income Taxes - Summary of Reconciliation of Statutory Income Tax Rate (Detail)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]      
United States statutory rate 21.00% 21.00% 21.00%
State tax, net of federal benefit 4.20% 1.00% 0.70%
Stock-based compensation (0.50%) (1.60%) 3.60%
Officer compensation (1.00%) (1.30%)  
Deferred rate change     0.30%
R&D credit 0.80% 1.80% 0.70%
Other (0.10%) 0.30% 0.70%
Change in valuation allowance (24.40%) (21.20%) (27.00%)